In various drilling and casing run-in applications, the tubular being lowered can move laterally with respect to the rig. Typically, the tubulars are suspended during run-in by an elevator attached to the rig, e.g., via bails extending from a top drive and/or traveling block. The elevator can swing via the bails; therefore, the elevator is able to move with the lateral movement of the tubular. However, the tubulars are also typically engaged by a spider flush-mounted or otherwise disposed on the rig floor in a rotary table. The spider is generally not suspended, and is typically not intended to be moved, in contrast to the elevator. Accordingly, lateral movement of the tubular generally translates to lateral movement with respect to the spider.
In such cases, the tubular can push against the spider, inducing a bending moment on the tubular, which can damage the tubular and/or other components of the rig. Moreover, even if the tubular does not damage itself or other components, it may remain off-center in the spider when the spider is needed to engage the tubular. Accordingly, the slips or bushings of the spider are caused to non-uniformly engage the tubular, since, due to the eccentric relationship between the spider and the tubular, some of the slips are positioned closer to the tubular than others. As such, the spider may attempt to bring the tubular back into alignment, which can induce bending moments on the tubular, as the inertia of the tubing resists the centering movement. Furthermore, especially for pneumatic spiders, the spider may be incapable of providing sufficient radial force so as to center the tubular. Accordingly, the tubular may be incompletely engaged by the spider, which can lead to the spider failing to adequately support the tubular, allowing the entire string to drop uncontrolled into the hole.
What is needed then are apparatus and methods for gripping a tubular with a spider, despite lateral movement of the tubular across a range of positions, while still enabling the spider to engage and support the string of tubulars.